The present disclosure relates to a fixing device heating and fixing an unfixed toner image formed on a sheet and an image forming apparatus including this fixing device.
Conventionally, an image forming apparatus of an electrographic manner, such as a printer or a copying machine, includes a fixing device heating and fixing an unfixed toner image formed on a sheet and consisting of a fixing member, such as a fixing roller or a fixing belt, and others. In the fixing device, in order to prevent adhesion of a toner onto a surface of the fixing member, a releasing agent, such as Mercapto-modified silicone oil, may be applied to the surface of the fixing member.
In the meanwhile, in the fixing device, there is a problem that, when the toner image is heated and fixed, a volatile substance included in a toner is volatilized and more offensive smell occurs as the volatilized quantity is increased. In addition, in the fixing device, there is also a problem that the volatile substance included in the releasing agent coated to the fixing member is volatilized and then an offensive smell occurs.
In order to cope with these problems, for example, an image forming apparatus may include an air discharging duct discharging an air in the vicinity of the fixing device to the outside of an apparatus body, an adsorbing agent carrying member provided in the middle of an air discharge path in the air discharging duct and an inhalant fan inhaling air in the air discharging duct. In this manner, it is proposed to adsorb and remove the volatile substance, and then, to discharge the air to the outside of the apparatus, thereby reducing the discharged quantity of the volatile substance.
However, in the image forming apparatus, ultra-fine particles and dust (less than 100 nm in particle size) may be discharged, but there is a problem that the ultra-fine particles cannot be sufficiently removed by removal of the volatile substance by the use of the adsorbing agent.
In order to solve such a problem, the image forming apparatus may have electrostatic dust collecting means electrostatically collecting the fine particles and dust produced in the apparatus. The electrostatic dust collecting means includes an electric discharge electrode and a dust collecting electrode and is installed in the air discharging duct disposed in the vicinity of the fixing device. In this manner, it is proposed to electrically charge the ultra-fine particles by electric discharge, and then, to collect them by the dust collecting electrode, thereby collecting the ultra-fine particles produced in the apparatus.
However, as the electrostatic dust collecting means mentioned above, in order to electrically charge the ultra-fine particles floating in air in the air discharging duct by electric discharge, there is a need to apply a large amount of current to a charger and to thereby carry out sufficient electric discharge. In addition, due to the electric discharge, a secondary product, such as ozone or NOx, may be generated and lead to environmental contamination. Thus, there is a need to provide a filter in order to collect the secondary product, and therefore, manufacturing costs is increased.
In addition, the ultra-fine particles may be contained in a wax adhered to the surface of the fixing member, but, if surface temperature of the fixing member is risen, the volatilized quantity and produced quantity of the ultra-fine particles volatilized from the wax may be exponentially increased. By contrast, if the surface temperature of the fixing member is lowered, there is a need to increase width of a fixing nip (a fixing time) in order to appropriately fix the toner image on the sheet. This causes upsizing of a fixing system or increasing of heat capacity, leading to lowering of energy saving property.